This invention relates to the provision of new low-k dielectric films for use in semiconductor and integrated circuit devices.
With the continuing decrease in size of microprocessors, low-k dielectrics are required to address some of the challenging problems such as cross-talk noise and propagation delay. These can become more critical to performance and more difficult to overcome as overall semiconductor device size is decreased while capabilities are increased. Among other aims, the industry is engaged in a search for dielectrics having a lower k value than dense silicon dioxide (k=3.9-4.2). The industry expects that low-k dielectric materials, especially materials with a k value lower than 3, and optimally lower than 2.2, will be needed for the design of devices with very small, e.g., 100 nm, features. In addition to the low k value, new dielectric materials must also meet integration requirements. These include a thermal stability in excess of 400xc2x0 C., good mechanical properties, good adhesion to a variety of surfaces and substrates, low water uptake and low reactivity with conductor metals at elevated temperatures.
A great number of materials have been proposed and studied as potential candidates, including some that demonstrated k values of 2 or lower. Two major classes of such materials are dense organic polymers and porous inorganic-based materials. Some dense organic polymers (e.g., highly fluorinated alkane derivatives such as polytetrafluoroethylene) may have sufficiently low k values, but they have the disadvantages of having relatively low thermal stability, thermal conductivity, and mechanical strength. In addition there is concern that they may react with conductor metals at elevated temperatures.
Among porous inorganic-based low-k materials, sol-gel silica has been extensively studied and is commercially available, for example from Allied Signal or Honeywell under the trademark Nanoglass. Sol-gel silica offers tunable k values, but some major concerns have been cited. It has a relatively low mechanical strength and a wide pore size distribution. Heat conductivity can be a shortcoming, especially with highly porous sol-gels, and this product also can possess a low resistance to electrical breakdown because of some randomly occurring large pores. In addition, its pore surfaces are initially hydrophilic, and require surface treatment to avoid absorption of moisture.
Recently, surfactant-templated mesoporous silica has been studied for low-k dielectric applications. Such materials are described, for instance, by Zhao, et al., Adv. Mater. 10, No. 6, 1380 (1998) and Baskaran et al., Adv. Mater. 12, No. 4, 291 (2000). This class of materials has more uniform pores than sol-gel silica (with a range of pore size of up to about 100 nm) and has been shown to have promising k values. Like sol-gel silica, however, there are concerns around low mechanical strength and hydrophilicity.
Hydrogen silsesquioxane films have also been under consideration for use as low-k dielectrics. Resins of this type, from which the films are produced, have been described in Lu et al., JACS 122, 5258 (2000) and a number of patents, including the recent U.S. Pat. No. 6,210,749. A series of these has recently been introduced under the trademarks FOx and XLK by Dow Corning. The FOx products are non-porous and have a k value of about 2.9. By incorporating porosity through a complex three-step process involving a high boiling organic solvent and ammonia gellation, XLK films with a lower k value of about 2.0-2.3 can be produced. Other Dow Corning products recently introduced include a trimethylsilane-containing gas (sold under the trademark Z3MS CVD) whose application by chemical vapor deposition can variously produce thin film dielectrics comprised of silicon oxycarbide or silicon carbide. Such technology is described, for instance, in U.S. Pat. No. 6,159,871. However, the k values of such films do not reach the lower end of the desirable range.
It would be advantageous, in light of these developments, to provide a low-k dielectric material that can be applied as a thin film, has relatively small pores (most preferably less than 5 nm) and uniform pore distribution, with the necessary mechanical strength to be treated by chemical and mechanical polishing (CMP). Preferably, also, such films will have low hydrophilicity or can readily be modified to have low hydrophilicity, so that they would be relatively unaffected by the presence of moisture.
This invention comprises the provision for use in semiconductor devices, of films that are comprised of silica zeolites, as well as methods for making such films, and articles such as semiconductor devices that use or include them.
In one aspect, the invention comprises a semiconductor device having a substrate and one or more metal layers or structures located on the substrate, and farther including one or more layers of dielectric material, in which at least one layer of dielectric material comprises a silica zeolite.
In a second aspect the invention comprises a method for producing a silica zeolite film on a semiconductor substrate comprising forming the film by in-situ crystallization, and, as a product, a semiconductor substrate or device having one or more films so produced.
In a third aspect the invention comprises a method for producing a silica zeolite film on a semiconductor substrate comprising forming the film by spin coating, and, as a product, a semiconductor substrate or device having one or more films so produced.
In another aspect the invention comprises a method for production of silica zeolite films having surface patterns, and, as a product, a semiconductor substrate or devices having one ore more films so produced.
In a further aspect the invention comprises certain silica zeolite films that are novel per se.